The present invention relates to a quick-coupling pipe fitting.
In the hydraulic sector it is frequently necessary to have fittings that can be coupled quickly to connect flexible or rigid pipes, in turn connected to a fluid supply and to a user.
Known quick-coupling pipe fittings are generally constituted by two elements, male and female, engaged on respective pipes to be connected to and coupled by screwing or by quick-action means.
According to a currently known art the female element is accomplished by means of a structure comprising an internal casing inserted at one end of an internally threaded nut for connection toward the supply or the user and by an external casing coaxial with said internal casing.
The internal casing supports an internal stem coaxial with an enlarged end. Externally to this, concentrically, so that an annular cavity is left, there is engaged a sealing bush that, under the elastic action of positioning springs and by engagement with the enlarged end of the stem, completely prevents the passage of the fluid in the cavity in the absence of coupling with the male element.
Concentrically and externally to the bush, there is a unit for cleaning the same constituted by a cup with a corresponding positioning spring.
To the internal casing, between it and a rear portion of the axial stem, there is fixed an annular spoked element in which there are obtained six small diameter holes for the passage of the fluid. As an alternative, so as to avoid the turbulence connected with the presence of holes having a small diameter, such annular element can be provided with at least two passage ports in the form of successive annular sectors, spaced by narrow spokes, along a circumference of said annular element.
The male element generally comprises an external casing provided with means for coupling with the female element at one end and an internally threaded nut at the other end for coupling toward the supply or to the user. Inside said casing, in a concentric position and so as to leave an annular cavity, there is a piston urged by corresponding positioning springs in a front closing position.
During the coupling between the female fitting and the male fitting, the cup of the female element is pushed by the external casing of the male element and, during its translation, carries the bush with it against the urging force of the corresponding positioning spring. At the same time the piston of the male element is urged to return inside the external casing of the male element against the force of the corresponding positioning spring up to a cavity opening position.
Coupling between the male and female element of the fitting, is generally obtained through quick-action coupling means. This creates a drawback since a comparatively quick wear of the fitting results in the coupling area.
Other types of fittings are also known wherein the coupling between the male and female element is accomplished by screwing, exploiting appropriate threads provided outside the female element and inside a terminal cavity of the male element.
These other types of fittings have the drawback of making it possible for dirt to be included inside the fitting itself. Such an effect is due to a non-flat shape of the terminal surface of the male element.